All-in-Fiber Dynamically Reconfigurable Orbital Angular Momentum Mode Sorting

Abstract

The orbital angular momentum (OAM) spatial degree of freedom of light has been widely explored in many applications, including telecommunications, quantum information, and light-based micromanipulation. The ability to separate and distinguish between the different transverse spatial modes is called mode sorting or mode demultiplexing, and it is essential to recover the encoded information in such applications. An ideal d mode sorter should be able to faithfully distinguish between the different d spatial modes, with minimal losses, and have d outputs and fast response times. All previous mode sorters rely on bulk optical elements, such as spatial light modulators, which cannot be quickly tuned and have additional losses if they are to be integrated with optical fiber systems. Here, we propose and experimentally demonstrate, to the best of our knowledge, the first all-in-fiber method for OAM mode sorting with ultrafast dynamic reconfigurability. Our scheme first decomposes the OAM mode in-fiber-optical linearly polarized (LP) modes and then interferometrically recombines them to determine the topological charge, thus correctly sorting the OAM mode. In addition, our setup can also be used to perform ultrafast routing of the OAM modes. These results show a novel and fiber-integrated form of optical spatial mode sorting that can be readily used for many new applications in classical and quantum information processing.

Azimuthal Modulation Instability, Breathers, and Solitons in Ring-Core Optical Fibers

“…In particular, specific ring-core fibers have been developed to optimize radial light confinement, thus supporting the propagation of a large number of OAM modes without detrimental mode couplings for efficient data transmission . The development of all-fiber schemes for stable OAM beam generation and propagation, but also supporting additional functions such as mode filtering, sorting, conversion, and amplification, is of considerable interest and is still facing several key challenges without the help of specific spatial devices in free space paths. − …”